Infill is stringing

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I have tried the triangle pattern and the quarter cubic pattern. Retraction is technically on but I don't see it retracting. I don't understand this as I always have retraction on and its always been very obvious when the filament retracts. Would Retraction Extra Prime Mount help with this? If so why is it highlighted orange when I give it a value? I am open to suggestions on what to do.

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Thanks for your response. Another question I have is why did it print the square cavity in the first print but not the second one. I am currently in cura trying to get it to see the cavity but it refuses. Any suggestions?

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The stringing on the infill generally is because they have the infill speeds pretty doggone fast. The UM infill philosophy is that infill is not as important to keep clean such as the walls are. I am not sure why the cavity is not showing in the second print. Separate slice?

If it is a different slice, you may have one, two or both options clicked on in the mesh fixes area:

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It may not suit everyone but, except for maybe some very large pieces, I always set infill speed to my print speed, indeed apart from 1st layer all my speeds are the same, and I have never seen stringing on the infill.

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3D-printed PLA may be more sturdy than ABS, because it has a much better layer bonding. It is less likely to split suddenly. I am often surprised at how much abuse my PLA models can have. Under load, they often survive longer than identical PET or NGEN models. But PLA has a couple of problems too, in my experience:

- In a hot car, or even in direct sunlight, it *will warp*, no doubt. So keep it out of the sun and out of hot cars and similar areas. Unless you use high-temp PLA.

- After a year or so, PLA gets harder and more brittle. It can still withstand quite some abuse, but it will no longer flex, and instead break suddenly. For example with snap-fit lockings, this is a problem, because you keep pushing hard until it locks or unlocks, and then it breaks. Thus you can not rely on flexibility to absorb sudden loads, and you can not design fragile springs, rather you need to design it like a Flintstone car model in concrete.

- Under a continuous high load, PLA suffers from creep deformation and micro-cracks. Just like most other hard plastics. So, make sure you store the model in a no-load condition, e.g. the wings supported by foam.

- You can not make a screw thread in it, it melts instead. Even very slow and light drilling is a problem. I just design holes in the models, and use nylon screws and nuts for clamping.

- I don't know about UV-stability, but most plastics deteriorate quite fast in UV-light. I guess it will be the same with PLA.

- Water is no problem, contrary to expectations based on the so-called bio-degradability of PLA. To test this, I have made a sift that is sitting for more than a year in my laboratory sink, and it still is okay. I also made one for colleagues, and theirs has been contaminated with blood and chemicals, and it is still okay also. So, your plane won't dissolve when flying in the rain, or landing in wet grass.

I am also curious about the flying characteristics, since usually a "square" plane (=about as long as wide) and a traditional layout (=with a big wing for lift in center of gravity, and small control surfaces far behind, like in sports planes), are considered to give the best control and flying characteristics, at normal subsonic speeds. So I wonder how a flying wing compares to that? In what aspects it would be better, and in what worse? I would guess lift is going to be better, but yaw-stability is going to be worse? But what about drag and maneuvrability, and stall characteristics?

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